This invention relates to a window glass antenna for a vehicle, and more particularly, to an antenna formed by supporting a substantially rectangular shaped transparent film of electrically conducting material on or within the upper region of a vehicle window panel.
The traditional mast or whip antenna has been used for several years to receive and transmit radio waves from a motor vehicle. Generally, these antennas have provided satisfactory performance, but they tend to distract from the aesthetic appearance of the vehicle, and several attempts have been made in the past to develop more inconspicuous type antennas that can be integrated directly into the structure of the vehicle. To this end, solid wires or opaque thick strips of conducting materials have been disposed on or within the window glass of vehicles to provide antennas for replacing conventional whip antennas. However, the antennas resulting from such efforts have unsuitably obstructed the view of the vehicle occupants, or have performed unsatisfactorily as compared to the traditional whip or mast type antenna.
More recently, attempts have been made to develop antennas formed by attaching thin transparent films of conducting materials to major central regions of vehicle windows. In general, the gain of these thin film antennas will increase as the film resistivity is decreased to reduce ohmic loss. For a given type of film, a larger conductivity (smaller resistivity) is usually achieved by increasing the thickness of the film, which in turn diminishes its transparency. Consequently, as film thickness is increased to improve antenna gain, a point will eventually be reached, where these antennas will no longer appear sufficiently transparent to vehicle occupants, and will be unacceptable because they occupy major central areas of windows. Thus, the trade off between acceptable antenna performance and suitable transparency is a factor limiting the usefulness of currently known configurations of thin film antennas for vehicle windows.
Therefore, a need exists for a thin film antenna, which does not have to occupy a major central region of a vehicle window, so that an acceptable antenna gain can be achieved by increasing the film conductivity, without making the antenna unsightly or unsuitably conspicuous to vehicle occupants.